Heat exchangers of the plate type are comprised of pairs of preformed plates joined to other pairs at their ends by integral bosses and separated at their middle section by air centers or corrugated fins, the plates and fins all being brazed together so that each pair of plates becomes a tube for carrying refrigerant, the bosses serving as a manifold for permitting refrigerant flow from one tube to another, and the fins facilitating heat exchange between the tubes and air flowing outside the tubes.
FIGS. 1, 2, and 3 depict such a heat exchanger. The plates 10 are mainly of a standard type having bosses or cups 12 and 14 on either end with apertures 16 communicating with adjacent cups to permit fluid flow therebetween. The boss 14 on one end is provided with a flange 18 around the aperture which nests in the aperture 12 of an adjacent plate. In some cases, to establish a particular flow pattern, a special plate having a blind boss 20, i.e. a boss with no aperture, is used instead of a flanged boss 14. Depending on the plate orientation the blind boss may be on either end. Moreover, each special plate is mated with a standard plate and either plate may be upstream depending on the orientation. Another type of special plate is the outside plate 22 on each side. The outside plate is bounded by a side plate 26 and a low center or fin 28 sandwiched between the outside plate 22 and the side plate 26. The low center 28 is half the thickness of the standard centers 30 which reside between the plate pairs. The special outside plate 22 has bosses with no flanges which are brazed directly to the side plate. U.S. Pat. No. 4,470,455 issued to Sacca describes such a plate type heat exchanger in detail.
The assembly of the plate type heat exchanger elements into a core ready for brazing has typically been carried out largely by hand operations. Specifically, the first step in the previous process is to assemble a fin element between two plates and form subassemblies by crimping the plates together where their bosses connect, and then manually stack such subassemblies along with side plates into a fixture which holds each subassembly in place.
It is desirable to enhance the assembly method to improve the efficiency of the assembly practice. In particular it has been found that the process is improved in terms of automation if it comprises joining the plates together into pairs that eventually become tubes, inserting the plate pairs and side plates into a fixture and then inserting the centers between the plates. It has been demonstrated that the automated assembly of plate pairs, air centers and side plates into fixtures is practical.
It is known to automatically assemble other styles of heat exchanger core as shown in the U.S. Pat. No. 4,321,739 to Martin et al. In Martin et al the tubes are first inserted into blocks carried by chains and the centers are then loaded between the tubes which are well spaced by the blocks. The tubes and centers are gathered together as the blocks are removed from one tube at a time. Thus tubes and centers are arranged in alternate rows and headers are joined to the ends of the tubes and tanks are joined to the headers to couple the tubes together. The tubes do not directly coact and they have smooth exteriors which facilitate the insertion of centers, as contrasted with the plate and center type which requires that the plates each mate with their neighbors as well as to sandwich the air centers. Further, the plate edges protrude in a way to interfere with center insertion so that large spacings between the plates would be required to permit center insertion. The large spacings necessitate a large gathering distance and also allow centers to get out of position so that centers can interfere with the coupling of the plates during the gathering process.